Normally, the brake actuating device for a disk brake is comprised of two expansion elements which are operated in opposition to one another. Thus, the two brake shoe linings are forced against a brake disk by means of the expanding motion of the two elements. In order to compensate for any play of the expansion elements due to the wear of the brake linings, it has been found to be advantageous to provide a compensating device between the expansion elements. The compensator functions in such a way that when any given stroke exceeds a predetermined value, the difference in the relative motion between the expansion elements as a result of lining wear is corrected automatically.
A wear compensator of the type mentioned above is shown and disclosed in German Pat. No. DE 27 09 762 and in the corresponding British Pat. No. 1,597,405.
This previous compensator for taking up wear on the brake shoe linings includes a pair of expansion elements which are interconnected to a connecting link. Along with the connecting link, an additional spring member is supported against one of the two expansion elements and is operatively connected with the other of the two expansion elements by a separate friction element. The support member in conjunction with the spring member set up a force in opposition to the relative motion of the expansion elements when the brake lining is forced against a brake disk. For this type of compensator construction, a third component is required in addition to the friction element and the spring element to secure the spring element.
In this previous known compensator, the spring element consists of a helical spring. Thus, the size of the spring must be relatively large since relatively great forces are necessary to return the expansion elements to their brake release position from an expanded or braking position. In order to increase this return force, one variation disclosed in the above noted German Pat. No. DE 27 09 762 features the use of an additional helical spring.
In the past, the return stroke of the expansion elements at a standard brake was, as a rule, executed by specially designed sealing rings for hydraulic disk brakes. Previously, the seals served a triple function, namely, the sealing function of the pressure chamber, the standard return function plus the added wear adjustment function. However, these three functions frequently overstress the sealing rings so that certain problems would occur, such as, insufficient return and therefore residual drag of the brakes resulted in too great a return (no adjustment) and therefore too great a stroke of operation, and as a result of the special design (return function) excessive leakage losses.
In the present invention, there is essentially only one function required for the sealing rings, namely, their actual sealing function, since the functions of returning and adjusting will be executed by the compensator. Further, in a unique design of the expansion elements in an intermeshing construction, the dimensions of the operating devices become smaller, which produces a further advantage in view of the fact that space is limited as is within the disk brakes.